Patent GB-924883-A (GB)
Title: Differential drive for vehicles
Filed: 1961-03-13
Abstract: 924,883. Reciprocating pumps. THORNTON PRODUCTS CO. March 13, 1961 [March 21, 1960; Sept. 8, 1960], No. 9168/61. Class 102(1). [Also in Group XXIV] In a limited-slip bevel differential gear in a vehicle, planets 54 meshing side wheels 50, 52 splined on axle shafts 28, 30 are outwardly urged to frictionally engage the input cage 32 and thereby restrict relative rotation of the axle shafts by pressure lubricating oil supplied by a reciprocating pump 68 which is responsive to axle shaft relative rotation. The planets 54 are mounted on arms 94 of a spider 56 the hub of which is bored to accommodate the pump 68 which comprises a cylinder 62 rotating with the axle shaft 30 and a piston 68 having followers 70 engaging a face cam 74 on the axle shaft 28 and longitudinal guide slots 72 in the cylinder 62. A cylinder, inlet port 84 is provided with a non-return valve which is of the needle or ball type or, as shown in Fig. 5, comprises a central flap portion 90 mounted by a spring arm 92 on a ring portion 88 retained in the cylinder by a spring 76 urging the followers 70 towards the face cam 74. The planets 54 are acted on by conical portions 102 of pistons 100 in chambers 96 which are bored in the spider arms 94 and fedfrom the pump through ports 108. The pistons are prevented from rotating in the chambers by pins 98 which also limit inward piston movement to ensure that oil pressure acts on the entire inner end faces of the pistons. To provide continuous pressure on the pistons during pumping, washers in the chambers 96 may cover the ports 108 to restrict oil return to the pump. Lubricating grooves 106 are provided in the piston conical portions 102 and in cylindrical portions 104 extending therefrom. The pump cylinder 62 is coupled to the axle shaft 30 by cruciform tongues and grooves which tongues may have T-portions for centring the cylinder in the side wheel 52. Oil is fed to the pump cylinder inlet port 84, via lines 80, 82 and the cruciform grooves in the axle shaft 30, from an annular chamber 78 which is filled from the differential housing either by conical centrifuging through the adjacent taper roller bearing of the differential cage 32, Fig. 1 (not shown), or by a vane or gear pump or a double acting, spring-loaded, piston pump, Figs. 8, 9 (not shown), which is reciprocated by an internal cam formed in the input bevel pinion driving the differential cage and has a maximum discharge pressure so as not to impair the action of the valve 90. In operation, on relative rotation between the axle shafts 28, 30 the piston 68 is reciprocated and pumps oil to the chambers 96 to outwardly urge the pistons 100 and thereby frietionally engage the planets 54 with the differential cage 32. Since the pistons 100 are prevented from rotation relative to the spider arms, the planets are gripped between the conical piston portions 102 and the differential cage. Oil returns to the differential housing, via the grooves 106 at a rate determined by the clearance between the pistons and chambers 100, 96, there being slight free differential action of the axle shafts, e.g. when the vehicle travels around a bend, when oil return past the pistons 100 is not exceeded by pump displacement. Washers may be provided between the differential cage and the outer faces of the planets and side wheels.